Hiya Miranda,
You don't sound like a B***h or self-pitying, you are in a very tough place, trying to support your parents, trying to care for your own family. Unfortunately if your siblings aren't prepared to do anything at the moment, then you do have to get on with it; try and not waste too much emotional energy on being angry with them, you need all your resources for your family and your parents.
Are there any specific problems that any of us can help with - there is a wealth of knowledge on TP, about financial considerations (Power of attorney, Court of Protection) and where to get help.
We all experience negative emotions, anger, sadness, jealousy, no-one on here will judge you, we are all doing our best to support someone that we love who has dementia.
I am so pleased that you have sorted out the 'posting' system.
Take care.
Amy